In recent years, the gate length of transistors, the size of contacts, and the like have been greatly decreased with downscaling of a semiconductor device. In order to suppress the short channel effect of such downscaled transistors, raising the contact regions of sources and drains with an epitaxial layer to separate the contact positions from corresponding channel regions has been devised. Further, in order to reduce the contact resistance in this case, impurities are introduced into the epitaxial layer at a high concentration. During introduction of the impurities, crystals in the top part of the epitaxial layer are damaged and are amorphized. The epitaxial layer is thermally treated to recrystallize the resultant amorphous part and to activate the impurities.
Although the epitaxial layer is recrystallized at the time of the thermal treatment, the top end part of the epitaxial layer contains many stacking defects. Accordingly, a problem occurs that the contact resistance between contact plugs and the epitaxial layer is not sufficiently lowered even when the contact plugs are formed on the epitaxial layer.